RECENT EXPERIMENTS ON FOG-SIGNALS 283 



tried at Shoeburyness. The most noteworthy result on 

 this occasion was the hearing of the sounds at the Mouse 

 Lighthouse, 8% miles E. by S., and at the Chapman Light- 

 house, 8% miles W. by N. ; that is to say, at opposite 

 sides of the firing-point. It is worthy of remark that, in 

 the case of the Chapman Lighthouse, land and trees inter- 

 vened between the firing-point and the place of observa- 

 tion. u This," as General Younghusband justly remarked 

 at the time, "may prove to be a valuable consideration if 

 it should be found necessary to place a signal station in 

 a position whence the sea could not be freely observed.' 7 

 Indeed, the clearing of such obstacles was one of the 

 objects which the inventor of the rocket had in view. 



With reference to the action of the wind, it was 

 thought desirable to compare the range of explosions pro- 

 duced near the surface of the earth with others produced 

 at the elevation attainable by the gun-cotton rockets. 

 "Wind and weather, however, are not at our command; 

 and hence one of the objects of a series of experiments 

 conducted on December 13, 1876, was not fulfilled. It is 

 worthy, however, of note that on this day, with smooth 

 water and a calm atmosphere, the rockets were distinctly 

 heard at a distance of 11/2 miles from the firing-point. 

 The quantity of gun-cotton employed was 7^ oz. On 

 Thursday, March 8, 1877, these comparative experiments 

 of firing at high and low elevations were pushed still 

 further. The gun-cotton near the ground consisted of 

 J^-lb. disks, suspended from a horizontal iron bar about 

 4% feet above the ground. The rockets carried the same 

 quantity of gun-cotton in their heads, and the height to 

 which they attained, as determined by a theodolite, was 

 from 800 to 900 feet. The day was cold, with occasional 



